The present invention relates to a powder sealing device of a powder beam processing machine for processing a workpiece by jetting a powder beam to the workpiece, more specifically, by allowing a solid/gas two-phase flow containing a powder (fine particles) in a high speed gas flow to collide with the workpiece.
A variety of powder beam processing machines have been known of a type in which a workpiece mounted on a pallet is processed by jetting a solid/gas two-phase flow containing a powder in a high speed gas flow to the workpiece. Such a machine includes, in a processing chamber, a processing table; a workpiece mounting pallet fixed on the processing table; and a processing nozzle for jetting a solid/gas two-phase flow to the workpiece mounted on the pallet, wherein the workpiece is processed by setting a positional relationship between the processing nozzle and the workpiece mounted on the pallet by relative movement of the processing table and the processing nozzle, and by jetting the solid/gas two-phase flow from the processing nozzle to a suitable position on the surface of the workpiece. The above-described relative movement of the processing table and the processing nozzle is adjusted outside the processing chamber via an operating shaft passing through the processing chamber. In such a machine, a powder sealing means is provided for preventing the powder from being leaked to the outside from a portion through which the operating shaft passes.
FIG. 1 is a typical view showing one example of a powder sealing device of a related art powder beam processing machine. In this figure, reference numeral 101 indicates an outer wall surface of a processing chamber; 102 is a rectangular cylinder body defining an opening portion in the outer wall surface 101; 103 is an operating shaft 103 extending from the outside to the inside of the processing chamber while passing through the cylinder body 102; and 104 is a thin film cylinder member formed of a flexible thin film material. With respect to the thin film cylinder member 104, one end portion thereof is formed into a rectangular shape and is air-tightly fixed around the outer periphery of the opening portion of the cylinder body 102, and the other end portion thereof is air-tightly mounted on the operating shaft 103 side. The thin film cylinder member 104 is adapted to seal the opening portion of the cylinder body 102 through which the operating shaft 103 passes.
In a powder beam processing machine, the thin film cylinder member 104 is generally drawn on the processing chamber side by a negative pressure generated in the processing chamber; however, since the opening portion of the cylinder body 102 in the related art powder beam processing machine is formed in a rectangular shape, the thin film cylinder member 104 becomes wrinkled by the corners of the opening portion, and the wrinkled portions are liable to be broken.
Since the related art powder beam processing machine does not include any means for discharging the powder having entered the thin film cylinder member 104 through the opening portion, the weight of the powder having entered the thin film cylinder member 104 is applied as a load to the thin film cylinder member 104, leading to such an inconvenience that the thin film cylinder member 104 may be broken or a mounting portion may be loosened.
In such a powder beam processing machine, a powder detecting sensor is provided near the thin film cylinder member 104 for detecting, if the thin film cylinder member 104 is broken, or if there is leakage of the powder from the thin film cylinder member 104. However, since the powder detecting sensor is provided in the atmospheric air, the powder leaked in the atmospheric air flies up in the air, and thereby it is difficult to detect the leakage of the powder, resulting in the poor detection accuracy.